| Title | Operational Characteristics of the Gaia Snow-Melting System in Ninohe, Iwate, Japan, Development of a Snow-Melting System Which Utilizes Thermal Functions |
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| Authors | Koji Morita and Makoto Tago |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | snow melting, GCHP, downhole coaxial heat exchanger, geothermal, solar heat, heat storage |
| Abstract | The authors have developed the Gaia Snow-Melting System, which utilizes the ground as a heat source and heat storage body. Another characteristic of the Gaia Snow-Melting System is the utilization of the Downhole Coaxial Heat Exchangers (DCHEs) proposed by the authors. In this system, solar heat absorbed in a pavement is recovered and stored in the ground over summertime. Hence, both geothermal heat and solar heat are used for melting snow in winter. The first Gaia Snow-Melting System was installed in December 1995 in Ninohe, Iwate Prefecture. The system covers an area of 266 m2. Three DCHEs, each 8.9 cm in outer diameter and 150.2 m long, and a heat pump driven by a 15 kW electric motor were used. Adjustments of the setting parameters of the operation control system were performed during the first winter and first summer of operation. Modifications of the control system were carried out before the second winter. In winters (not including the first winter), the average coefficients of performance (COP) for the heat pump have been 4.2 to 4.3 and the average specific heat extraction rates 80 to 83 W/m. The Gaia system's annual electric power consumption per unit area has been less than 20 % that of the electric heating cable systems used in the same city. The cumulative heat charged into the ground from the onset of operation until the end of November 1998 was greater than that extracted from the ground during the same period. Temperature profiles measured at an observation DCHE have changed year by year. However, the average temperature in the DCHE before the winter of 1998 was almost the same as that of the initial temperature profile in the DCHE. A more appropriate design and higher performance will be realized in the next system. |